Field of the Invention
The present invention relates to an aqueous ink set, an ink jet recording method and an ink jet recording apparatus.
Description of the Related Art
In recent years, an ink used for an ink jet recording method has been required to furthermore improve optical density and bleeding resistance of an image recorded. Plain paper among recording media includes those of various types with different ink permeabilities. An ink capable of recording an image with both optical density and bleeding resistance at a high level regardless of the type of plain paper is required.
There is a proposal of an ink using a self-dispersible pigment to a particle surface of which a functional group having high reactivity with respect to calcium is bonded and capable of improving the optical density of the resulting image, wherein the functional group is selected on the basis of calcium index which is an index of reactivity with respect to calcium (PCT Japanese National Publication No. 2009-515007). There are also proposals of an ink which contains a self-dispersible pigment to a particle surface of which a functional group containing a phosphonic acid group is bonded and a salt, and is capable of improving the optical density of a resulting image (Japanese Patent Application Laid-Open No. 2012-052095 and Japanese Patent Application Laid-Open No. 2012-052097). There is further a proposal of an ink with improved bleeding resistance by using a self-dispersible pigment whose migration rate measured by paper chromatography has been specified (Japanese Patent Application Laid-Open No. 2003-096367).
The optical density of an image recorded is somewhat improved by using the self-dispersible pigment proposed in PCT Japanese National Publication No. 2009-515007 or the specific salts proposed in Japanese Patent Application Laid-Open No. 2012-052095 and Japanese Patent Application Laid-Open No. 2012-052097. However, results of an investigation by the present inventors have revealed that the bleeding resistance may be insufficient in some cases. In addition, the ink proposed in Japanese Patent Application Laid-Open No. 2003-096367 contains a lot of a highly permeable water-soluble organic solvent, so that the optical density of an image recorded is insufficient. Further, the ink easily retains in a cap for capping a recording head provided in an ink jet recording apparatus. Thus, there has been room for improving the reliability of the ink. The “cap for capping the recording head provided in the ink jet recording apparatus” is also referred to as “cap” merely.